The present invention relates to novel zonal geranium plants, Pelargonium hortorum—interspecific, having a trailing habit and dark-red to burgundy pigmented flower petals, a growth habit similar to an ivy geranium, green leaf color, tolerance to high light and temperature and non-sensitivity to edema. The present invention also relates to methods for creating novel Pelargonium hortorum—interspecific plants having pigmented flower petals. The present invention relates to a new and distinctive method of combining Pelargonium plants to produce new, distinct interspecific Pelargonium varieties. All publications cited in this application are herein incorporated by reference.
Pelargonium hortorum belongs to the family Geraniaceae. The exact origin of Pelargonium hortorum is unknown, but probably resulted from inter-crossing between several species native to South Africa including P. zonale, P. inquinans, P. scandens and P. frutetorum. Geraniums rank as one of the highest number of plants in terms of units sold among potted flowering plants and in terms of wholesale value. The traditional zonal geranium product has red, salmon, violet, white or pink flowers, green foliage, and is grown in 4-inch, 6-inch or gallon pots—the 4-inch product remains the bulk of the market.
There are basically 5 different types of Pelargonium in the market today. Zonal geraniums are the standard version of geraniums that are propagated vegetatively, by cuttings. Typically, they are tetraploid and have large 4-inch to 6-inch round flower heads with each flower having double blooms held well away from the plant foliage. The leaves are also large and sometimes up to 4-inches across. The plant habit tends to be rather upright and well branched generally growing to about 18-inches in one growing season. They are called zonal geraniums because many of them have zones or patterns in the center of the leaves. Varieties with self-branching habit and compact growth make tidy, well-shaped plants with a show of color all summer long. Some of the varieties have unusually dark green foliage which makes a particularly striking contrast to the colorful flower heads held above the foliage.
Seed geraniums are diploid plants grown from seed. They produce a more compact version of the zonal geranium, but with smaller single blooms on smaller 3-inch to 4″ heads of blooms. These plants form low, compact mounds typically under a foot tall and wide. Seed geraniums are most often used in large landscape plantings and in smaller containers such as window boxes.
Named for both their habit and their ivy-like leaves, ivy geraniums typically have leaves that are stiff and shiny. The branches are long and trailing. Flower clusters on ivy geraniums are about 2-inches to 3-inches across. Plants can spread over 2-inches in one season. Ivy geraniums are great in hanging baskets and in window boxes and other containers.
Regal geraniums are great for early season color, but it is important to know they do not like the heat of summer and so they reduce the number of blooms they provide until the cool weather of fall.
Valued for their unique fragrances, scented geraniums are also worth growing for their distinctive foliage. While some varieties do occasionally bloom, scented geraniums usually are not grown for their flowers. The plant habit varies widely from one variety to another, as do leaf size, shape, color and texture.
Years ago, growers retained selected plants from the seasonal crops as stock plants for the subsequent season. These plants were maintained either in the greenhouse or planted outside for the summer and fall, then repotted and brought inside before the first frost. Cuttings were taken in winter, rooted, and maintained under minimum conditions until early spring for forcing. Several events precipitated a drastic change in this procedure. The economics of greenhouse space utilization combined with the development of “fast cropping” made the old procedures impractical. The development of serious systematic diseases almost always lead to the demise of the crop, mainly Xanthomonas campestris pv. pelargonii (bacterial wilt).
Today, vegetative material almost exclusively comes from specialized propagators that use culture-virus-indexing and other laboratory procedures to eliminate bacterial wilt and other systematic organisms such as vascular wilt, bacteria, virus, and fungi.
With any successful breeding program, there are numerous steps in the development of novel, desirable plant germplasm. Plant breeding begins with the analysis and definition of problems and weaknesses of the current germplasm, the establishment of program goals, and the definition of specific breeding objectives. The next step is selection of germplasm that possess the traits to meet the program goals. The goal is to combine in a single variety an improved combination of desirable traits from the parental germplasm. For the horticultural industry, these important traits can include novel colors, resistance to diseases and insects, tolerance to drought and heat, or superior garden performance.
Traditionally, new traits are introduced into a breeder's germplasm through the combination of two individual plants that each possesses desirable characteristics. The parental lines are crossed and the progeny are evaluated for the presence of the desirable traits. Evaluation involves observing the progeny under different environmental conditions and at multiple times for the purpose of identifying any new expected and unexpected variations that may be useful. The new hybrid lines may be reproduced sexually or asexually. In the ornamental flowering plant industry, often times a particular characteristic, or set of characteristics, is not stable through several generations of sexual reproduction. The breeder may use asexual reproduction to propagate the variety, thus avoiding sexual recombination of traits and keeping the line uniform and stable.
The parents in a hybridization do not have to belong to the same species. Sometimes different species of the same genus will combine sexually in an interspecific cross. In some cases, different species readily combine in an interspecific cross to produce a hybrid plant. In other cases, barriers to combinability exist between species.
In order to introduce valuable economic traits such as disease resistance, flower shape and color, and heat or cold tolerance, from non-commercial species into the cultivar assortment, it is essential to overcome interspecific crossing barriers. Various techniques have been attempted to deal with some of these barriers, including in vitro isolated ovule pollination, in vitro embryo rescue, and ovary-slice and ovule culture. However, these techniques do not overcome the problem of chromosome mismatching and loss of chromosomes during meiosis and mitosis, barriers commonly encountered in interspecific crosses.
Sexual reproduction between individuals with different chromosome numbers, often the case in interspecific crosses, can be problematic. During sexual reproduction, each gametic chromosome must pair with its partner from the other parent's gamete. In this manner, the offspring receive a full complement of chromosomes, half of which originate from each parent. If the chromosome number of the parents is different, chromosome pairing does not occur correctly. Results of mismatched chromosome pairing may include the interspecific cross not producing offspring, the offspring produced being sterile, or the offspring produced being barely fertile.
One method for dealing with poor interspecific hybrid fertility is to look for naturally occurring 2n-gametes produced by the interspecific hybrid. Some plants frequently produce 2n-gametes, but others rarely do. Finding these 2n-gametes can be very difficult and time-consuming. Another method for restoring interspecific hybrid fertility is to double the chromosome number of the hybrid to produce an amphidiploid. This can be done using the chemical colchicine, which inhibits microtubule formation during cell division. When treated with colchicine, a cell's chromosomes are copied in preparation for mitosis as normal, but the lack of microtubules prevents cell cleavage. The result is an undivided cell that contains double the normal complement of the organism's chromosomes. The colchicine-treated cell is then regenerated into a full plant in which each cell has its chromosomes doubled. If an individual with mismatched chromosomes is treated with colchicine, its chromosomes will be doubled, thus creating a matching partner chromosome that is able to match up properly during sexual reproduction. The procedure can restore fertility to a formerly sterile individual and the newly fertile, amphidiploid plant can then produce segregating offspring that can be observed for further traits. Colchicine may also be used to double the chromosome number of a normal, cultivated plant so that the plant may be able to readily combine with another plant that has a different number of chromosomes. There is a range of ploidy levels among Pelargonium type. For example, cutting geraniums are typically tetraploid while seed geraniums are diploid.
Additionally, choice of breeding or selection methods depends on the mode of plant reproduction, the heritability of the trait(s) being improved, and the type of cultivar used commercially (e.g., F1 hybrid cultivar, pureline cultivar, etc.). For highly heritable traits, a choice of superior individual plants evaluated at a single location will be effective, whereas for traits with low heritability, selection should be based on mean values obtained from replicated evaluations of families of related plants. Popular selection methods commonly include pedigree selection, modified pedigree selection, mass selection, and recurrent selection.
The complexity of inheritance influences choice of the breeding method. Backcross breeding is used to transfer one or a few favorable genes for a highly heritable trait into a desirable cultivar. This approach has been used extensively for breeding disease-resistant cultivars. Various recurrent selection techniques are used to improve quantitatively inherited traits controlled by numerous genes. The use of recurrent selection in self-pollinating crops depends on the ease of pollination, the frequency of successful hybrids from each pollination, and the number of hybrid offspring from each successful cross.
Each breeding program should include a periodic, objective evaluation of the efficiency of the breeding procedure. Evaluation criteria vary depending on the goal and objectives, but should include gain from selection per year based on comparisons to an appropriate standard, overall value of the advanced breeding lines, and number of successful cultivars produced per unit of input (e.g., per year, per dollar expended, etc.).
Promising advanced breeding lines are thoroughly tested and compared to appropriate standards in environments representative of the commercial target area(s) for three or more years. The best lines are candidates for new commercial cultivars; those still deficient in a few traits can be used as parents to produce new populations for further selection.
These processes, which lead to the final step of marketing and distribution, require several from the time the first cross is made. Therefore, development of new cultivars is a time-consuming process that requires precise forward planning, efficient use of resources, and a minimum of changes in direction.
A most difficult task is the identification of individuals that are genetically superior, because for most traits the true genotypic value is masked by other confounding plant traits or environmental factors. One method of identifying a superior plant is to observe its performance relative to other experimental plants and to a widely grown standard cultivar. If a single observation is inconclusive, replicated observations provide a better estimate of its genetic worth.
Pedigree breeding and recurrent selection breeding methods are used to develop cultivars from breeding populations. Breeding programs combine desirable traits from two or more cultivars or various broad-based sources into breeding pools from which cultivars are developed by selfing and selection of desired phenotypes. The new cultivars are evaluated to determine which have commercial potential.
Pedigree breeding is used commonly for the improvement of self-pollinating crops. Two parents that possess favorable, complementary traits are crossed to produce an F1. An F2 population is produced by selfing one or several F1. Selection of the best individuals can begin in the F2 population; then, beginning in the F3, the best individuals in the best families are selected. Replicated testing of families can begin in the F4 generation to improve the effectiveness of selection for traits with low heritability. At an advanced stage of inbreeding (i.e., F6 and F7), the best lines or mixtures of phenotypically similar lines are tested for potential release as new cultivars.
Mass and recurrent selections can be used to improve populations of either self- or cross-pollinating crops. A genetically variable population of heterozygous individuals is either identified or created by intercrossing several different parents. The best plants are selected based on individual superiority, outstanding progeny, or excellent combining ability. The selected plants are intercrossed to produce a new population in which further cycles of selection are continued.
Backcross breeding has been used to transfer genes for a simply inherited, highly heritable trait into a desirable homozygous cultivar or inbred line which is the recurrent parent. The source of the trait to be transferred is called the donor parent. The resulting plant is expected to have the attributes of the recurrent parent (e.g., cultivar) and the desirable trait transferred from the donor parent. After the initial cross, individuals possessing the phenotype of the donor parent are selected and repeatedly crossed (backcrossed) to the recurrent parent. The resulting plant is expected to have the attributes of the recurrent parent (e.g., cultivar) and the desirable trait transferred from the donor parent.
Descriptions of other breeding methods that are commonly used for different traits and crops can be found in one of several reference books (e.g., Allard, 1960; Simmonds, 1979; Sneep et al., 1979; Fehr, 1987).
Therefore, there is a need for a method that combines Pelargonium species so that new important traits can be introduced into novel Pelargonium hybrids.
The foregoing examples of the related art and limitations related therewith are intended to be illustrative and not exclusive. Other limitations of the related art will become apparent to those of skill in the art upon a reading of the specification.